This invention relates to an inking apparatus for a printing press, which can easily control the contact pressure of ink form rollers on the surface of a printing plate mounted on a plate cylinder, thus eliminating the need for readjustment of the contact pressure after skewing adjustment of the plate cylinder.
Heretofore, an inking apparatus mounted on printing presses such as a rotary printing press is provided with an ink fountain and a plurality of rollers. Ink charged in the ink fountain is picked up by rotation of ink fountain rollers and is applied as a film of ink onto the surface of the forming rollers. Furthermore, the film of ink is kneaded and spread in all directions while being transferred between the rollers, and is then supplied by the ink form rollers to the plate surface on the plate cylinder.
In the above inking apparatus, the contact pressure between the ink form rollers and the plate surface, that is, a so-called nip pressure, has tended to vary with changes in diameter of the ink form rollers due to thermal expansion, abrasion, and finishing of the plate cylinder. Since the nip pressure largely affects the quality of printed matter, the inking apparatus is provided with a nip pressure adjusting device to adjust the nip pressure in the preparation stage for printing or during printing.
As such a nip pressure adjusting device, there has been known, for example, one which is disclosed in Japanese Patent Publication Laid-open No. 58-175663/1983. In this device, ink form rollers are individually supported by swingable roller arms, and the roller arms are urged by spring members with adjustable urging force so that the ink form rollers are pressed against the plate surface.
Furthermore, when the printing plate is mounted to the plate cylinder of the printing press, the printing plate may be slightly skewed with respect to the plate cylinder, and the individual ends of the printing plate may become shifted peripherally from each other in the reverse directions, resulting in a mis-registration between the right and left sides. In this case, eccentric bearings rotatably supporting the rotary shaft of the plate cylinder on the frames of the printing press are turned to correct the error of registration, that is, so-called skewing adjustment is made.
However, with the above nip pressure adjusting device, skewing adjustment of the plate cylinder varies the already adjusted nip pressure. Then, the nip pressure must be adjusted again, requiring additional time and labor.